1. Field of the Invention
The present invention relates to machines for receiving, distributing and laying down paving material.
2. Description of Related Art
In building and rebuilding roads, paving material is typically delivered to the work-site by truck. Often the trucks dump the paving material directly into receiving hoppers of the road construction machines. In some cases, the paving material is windrowed on the surface by the trucks and the road construction machines pick up the windrow of paving material.
Whether the paving material is dumped into hoppers or windrowed, a problem exists in balancing the delivery of paving material by the trucks with the use of the paving material by the road construction machines. Increasing the capacity of receiving hoppers the road construction machines is one way to address this problem. Of course, there are practical limits on the length and width of such hoppers. In some machines, the capacity of the receiving hopper has been increased by extending the hopper walls vertically. Vertical extension of the hopper, however, creates problems in dumping paving material into the hopper.
Another problem relates to the traction of such machines. Small wheels or hard rubber bogies are often used for the front wheels and large wheels are typically mounted at the rear. The paving material load on the machine may place a substantially amount of the weight on the front wheels Such machines may be equipped with four-wheel drive, but the weight may cause small front tires to sink and lose traction.
Yet another difficulty relates to the four-wheel drive system itself. Positive traction electro-hydraulic systems are in use to control drive to each wheel based upon the rotational speed of each wheel. When the machine is in a turn, however, the hydraulic flow to each wheel cannot be equalized in order to achieve optimal traction.
The outside wheel in a turn has to travel a greater distance than the inside wheel. If the hydraulic flow to each wheel is equalized, then the inside wheels and the outside wheels would not be forced to make the turn in the same amount of time. One problem with traction in turns, therefore, is how to make the inside wheels and outside wheels cover their respective distances in the same amount of time.